In the glass container industry, small cracks, or fracture in the glass are referred to as “check defects”. Checks can range from sub millimeters to several hundred millimeters and can be oriented at any direction from vertical to horizontal. Glass is not a crystalline structure by nature, but most cracks propagate roughly along a plane of some orientation in space mostly determined by the shape of the glass at that location. Most of these crack defects will drastically weaken the bottle, often causing it to rupture or to leak. Therefore, it is very likely that a bottle manufacturer will remove a container with a check before it reaches filling plants. Checks appearing near the mouth of the containers are called finish checks. In the glass bottle industry, the term “container finish” refers to the portion of the bottle that defines the mouth, threads or beads, and the ring. The upper surface of the mouth is referred to as the sealing surface.
Another anomaly, which can also be present are bubbles. A bubble results when gas is trapped in the glass. When the bubbles are large they are referred to as a blister and when the bubbles are small, they are referred to as a seed. The presence of bubbles, while affecting the appearance of the bottle, do not necessarily require the rejection of the bottle and an operator may allow such a bottle to be packed. For purposes of this application, the word blister will include a seed.
The following U.S. Pat. Nos. 4,701,612, 4,945,228, 4,958,223, 5,020,908, 5,200,801, 5,895,911, 6,104,482, 6,211,952, and 6,275,287 all relate to devices that detect defects in the finish of a container.